function Snake(el)
{
    this.el=el
    this.len=20
    this.direction='right'
    this.snakeObj=[
        {x:3,y:2,color:'red',el:null},
        {x:2,y:2,color:'blue',el:null},
        {x:1,y:2,color:'blue',el:null}
    ]
    this.init()
}
Snake.prototype.init=function(){
    
}
Snake.prototype.remove=function(){
    for(let i=0;i<this.snakeObj.length;i++){
        if(this.snakeObj[i].el) this.el.removeChild(this.snakeObj[i].el)
    }
}
Snake.prototype.createS=function(){
    this.remove()
    for(let i=0;i<this.snakeObj.length;i++){
        let divObj=document.createElement('div')
        divObj.style.width=this.len+'px'
        divObj.style.height=this.len+'px'
        divObj.style.borderRadius='50%'
        divObj.style.background=this.snakeObj[i].color
        divObj.style.position='absolute'
        divObj.style.left=this.snakeObj[i].x*this.len+'px'
        divObj.style.top=this.snakeObj[i].y*this.len+'px'
        this.snakeObj[i].el=divObj//保存蛇
        this.el.appendChild(divObj)
    }
}

Snake.prototype.move=function(){
    // for(let i=0;i<this.snakeObj.length;i++){
    //     this.snakeObj[i].x++
    // }
    for(let i=this.snakeObj.length-1;i>0;i--){
        this.snakeObj[i].x=this.snakeObj[i-1].x
        this.snakeObj[i].y=this.snakeObj[i-1].y
    }
    switch(this.direction){
        case 'top':
            this.snakeObj[0].y--
            break;
        case 'bottom':
            this.snakeObj[0].y++
            break;
        case 'left':
            this.snakeObj[0].x--
            break;
        case 'right':
            this.snakeObj[0].x++
            break;
    }
    this.createS()
}
